Friday, March 10, the National Oceanic and Atmospheric Administration and the Scripps Institution reported their jointly operated observation post on Mauna Loa has recorded CO2 levels at more than 400 parts per million. This is the first time the Hawaiian post has recorded a daily average breaking this milestone. In 1958, the first measurement ever taken at Mauna Loa was 315 ppm. That measurement was taken by Charles David Keeling, creator of the Keeling Curve—a plot line of CO2 levels at Mauna Loa recorded from that year to present day.

This meteoric rise in CO2 is a primary source of concern for climatologists and environmentalists alike. Estimates indicate that pre-industrial levels of carbon dioxide were only about 280 ppm according to the NOAA. The Guardian reports the last time our planet saw levels comparable to today’s measurements was during the Pliocene Epoch three to five million years ago. The Pliocene period saw significant die-offs of reef systems and thick forests growing far into the northernmost reaches of what is currently tundra.

Former Vice President Al Gore was quick to weigh in after the news was released, speaking through Huffington Post’s Green Blog, which features many contributing authors in environmental issues.

Gore paints a bleak picture, saying that, “[past] favorable conditions on Earth could become a memory if we continue to make the climate crisis worse day after day after day.”

May marks a seasonal high point for CO2 emissions in Hawaii due to air currents carrying the released CO2 of decaying plants, therefore the daily average is likely to sink back below 400 ppm once more. Arctic stations, however, are already holding steady at over 400 ppm.

Physicist Joanna Haigh, head of atmospheric physics at Imperial College, pointed out, “the value 400 ppm of CO2 has no particular significance for the physics of the climate system… However, this does give us the chance to mark the ongoing increase in CO2 concentration and talk about why it’s a problem for the climate.”

Gore, among others, seems to share Haigh’s thoughts in consensus: 400 ppm is just primarily a statistical measurement.